This invention relates to a control apparatus for ensuring safety of a vehicle run having a first control device regarding a running stability of a vehicle and a second control device for avoiding a vehicle run from being involved in a dangerous state, in particular, relates to measures against a fail of the first control device.
Conventionally, as a device for avoiding a vehicle run from being involved in a dangerous state, there have been known an automatic braking device and an automatic steering device. The automatic braking device is so composed to continuously detect a distance and a relative velocity between a vehicle and a forward vehicle by using an optical method, ultrasonic waves or the like, judge whether there is a possibility of contact between the vehicle and the forward vehicle by the detected distance and relative velocity, and operate an actuator to automatically apply a braking force to each wheel when it is judged that there is the possibility of contact as well as, for example, as disclosed in Japanese Patent Application Open Gazette No. 54-33444. The automatic steering device is so composed that when judged is that there is the possibility of contact in the automatic braking device, a running path for avoiding the contact is expected, and front wheels are automatically steered so that a vehicle can run along the path, for example, as disclosed in Japanese Patent Application Open Gazette No. 64-26913.
As a device regarding a running stability of a vehicle, there have been generally known a four wheel steering system (4WS) for steering rear wheels in a same phase and in a same direction as steering direction of front wheel at steering front wheels, an anti-skid braking system (ABS) for restraining a considerable braking force at braking a vehicle, a four wheel driving device (4WD) and the like. Such kinds of devices are in general so composed that whether each element composing the devices correctly works is detected using a sensor and safety measures to raise an alarm or the like at a fail of the element is provided (see U.S. Pat. Nos. 5,082,080 and 4,840,243).
When the automatic braking device or the automatic steering device works, a vehicle run is easy to fall into an unstable state. Accordingly, such devices are preferably provided on a vehicle together with a device regarding a running stability of a vehicle such as the 4WS, the ABS, the 4WD or the like. However, even though the device for avoiding a vehicle, run from being involved in a dangerous state and the device regarding a running stability of a vehicle are provided together, working of the automatic braking device or the automatic steering device at a fail of the device regarding a running stability makes a vehicle run unstable.